A light emitting diode (LED) has advantages such as low power, high efficiency, high luminance, and long lifetime and is thus mainly provided in the form of a package in electronic parts, but is disadvantageously susceptible to static electricity or inverse voltage. In order to utilize an LED in the presence of static electricity or inverse voltage, a Zener diode or a varistor is connected parallel to an LED chip.
However, a process of integrally packaging a Zener diode or a varistor with an LED chip is problematic because of a limited space and an increased number of processes due to additional processing, and an enlarged size and high manufacturing cost due to additional mounting.
Also, by means of a Zener dioder or a varistor disposed to be flush with the LED chip, light produced from the LED chip may be scattered and refracted, making it difficult to efficiently control a luminous view angle. Therefore, a process of embedding a Zener diode in a substrate is being adopted.
A device-incorporated substrate includes inner and outer electrodes, and the inner electrodes are printed between the sheets of the substrate and then sintered. The outer electrodes are connected to the inner electrodes.
However, a substrate disclosed in Korean Patent Application Publication No. 2013-0007693 may cause shrinkage deformation in a firing process depending on the type of material for the substrate. Furthermore, the shrinkage rate of the substrate is not uniform, making it difficult to manufacture a substrate that satisfies a precise dimension standard. Moreover, reducing the shrinkage rate of the substrate may be complicated, undesirably deteriorating productivity. Also, as the substrate itself is not enhanced in mechanical strength, utility of the substrate may decrease.